JPH01142413A - Encoder apparatus - Google Patents

Abstract

PURPOSE:To obtain a plurality of signals from one MR element group, by differentiating and combining the saturated magnetic fields of the MR elements in accordance with specified rule. CONSTITUTION:A substrate 1 is arranged so as to face a magnet 2, which is magnetized in a specified pattern. MR elements 6 and 6' are formed on the substrate 1. The widths and the lengths of the MR elements 6 and 6' are different to each other. As a result, saturated magnetic fields are different. The MR elements 6 and 6' are aligned at a specified pitch and connected in series. In this constitution, a plurality of the MR elements 6 and 6' correspond to one magnetization of the magnet 2. Therefore, a plurality of output signals can be obtained. Since the pitch of the MR elements 6 and 6' can be determined accurately by a lithography technology, the detecting accuracy can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an encoder device, and particularly to an encoder device using a magnetoresistive element (hereinafter referred to as an MR element).

[Prior Art] Conventionally, there have been two types of encoder devices of this type: a magnetic type and an optical type.Furthermore, the magnetic encoder devices include a coil generation type using magnetic induction and a type using an MR element. be.

An encoder device using an MR element is Ni-Fe.

Ni-Co5 is patterned by a thin film formation method, and changes in the applied magnetic field are detected by changes in resistance of these thin film elements. In an encoder device using an MR element, a permanent magnet or the like may be used as a magnetic field generating means for the detected object. Therefore, it is possible to obtain an encoder device that is simpler in construction and more durable than a photosensor or the like that requires a power source such as an LED, and also requires a consumable light source.

[Problems to be Solved by the Invention] In the encoder device using the MR element as described above, the output resolution is one or two for one magnetic pole.
one for each magnetic pole.

Therefore, in order to obtain a high-resolution output, it is necessary to increase the number of magnetized permanent magnets per unit protrusion, that is, to reduce the magnetized pitch.

However, there is a limit to reducing the magnetization pitch, and furthermore, it is difficult to do so with high precision. Therefore, it has been difficult to obtain an encoder with high resolution and high precision.

Furthermore, in order to obtain a plurality of output signals, the same number of MR elements as the number of output signals are required, so a plurality of MR elements are arranged on the same substrate.

However, arranging a large number of MR element groups increases the size of the entire apparatus. Furthermore, the number of extraction patterns increases as the number of MR elements increases, and as a result, for extraction patterns for extracting output signals obtained from a large number of MR elements,
Noise based on the electromotive force induced by the movement of the magnetic field of a magnet or the like facing the MR element increases.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a high-resolution and high-precision encoder device using an MR element, thereby making it possible to obtain a plurality of output signals.

[Means for Solving the Problems] In view of this objective, the encoder device of the present invention is an encoder device that detects the relative position of a detected object and a detected object, and which detects the relative position of a detected object and a detected object. A detection object and a plurality of magnetoresistive elements whose saturation magnetic field is sufficiently smaller than the magnetization magnetic field of the detection object and arranged in parallel at a pitch smaller than the magnetization pitch are placed opposite to the detection object and arranged in parallel. The detection body includes a plurality of magnetoresistive elements whose saturation magnetic fields are varied according to a predetermined rule.

[Function] In the above configuration, since the magnetized 8i magnetic field is sufficiently larger than the saturation magnetic field of the magnetoresistive element, the detection output by the MR element becomes steep, and more MR Since the elements are compatible, resolution can be increased and multiple output signals can be obtained. Furthermore, since the pitch of the MR elements can be determined very accurately by photolithography, detection accuracy is also improved.

[Example] An embodiment of the present invention will be described below.

Figure 1 (a), (b), (c), (d)
1A and 1B are diagrams for explaining a rotary encoder that is a first embodiment of the present invention. FIG. 1A is a cross-sectional view of this rotary encoder, and FIG. (c) is a diagram showing the magnetization signal of the magnet in (b), (d) is a diagram showing how the magnet is magnetized.
1 is a diagram showing a pattern of an MR element which is a detection object.

In Fig. 1(a), the magnetic flux emitted from magnet 2 is MR
It passes through the substrate l on which the element is formed, and then returns to the magnet 2 through the stator yoke 3 and back through the substrate l. The magnetization curve of the magnet 2 may be a sinusoidal wave, nine trapezoidal waves, etc., and the following description will be made assuming that it is a sinusoidal wave. As shown in FIG. 1(b), the surface of the magnet 2 facing the substrate 1 is magnetized so that north poles and south poles are arranged alternately. In this embodiment, it is magnetized into 8 poles, and the width angle 0° of the output pulse is 2 sin-' (Hs/Ho) or 2 sin-'(Hs'/Ha).

In the encoder device of this embodiment, all the MR elements 6 and 6' are connected in series as shown in FIG. 1(d).

The MR elements 6.6' in the MR element group in FIG.
The element 6 and the MR element 6' are different. Now, if the length of the MR element 6' is the intersection and the width is W, then the length of the MR element 6 is bl,
The width can be expressed as aw. Each MR element 6, 6' has a signal magnetic field shown in FIG. 2 and a pitch p=π/(n+1
) (n = 0.1, 2......). M
Since the saturation magnetic field of the R element is sufficiently smaller than the signal magnetic field of the magnet 2, the resistance value change of the MR element group with respect to the signal magnetic field of the magnet 2 is as shown in FIG. 3(a).

Therefore, constant current ■. These elements 6. ...The width angle of the output pulse at 0° is 2sin-'' (Hs/Ho) or 2sin-'(Hs'/Ho).

In the encoder device of this embodiment, the MR elements 6 and 6' are all connected in series as shown in FIG. 1(d).

The MR elements 6.6' in the MR element group in FIG. 1(d) have different widths and lengths, that is, the saturation magnetic field is MR
The element 6 and the MR element 6' are different. Now, if the length of MR element 6' is W and the width of sentence 1 is W, then the length of MR element 6 is bl,
The width can be expressed as aw. Each MR element 6, 6' has a signal magnetic field shown in FIG. 2, and a pitch P=π/(n+1
) (n = 0.1, 2......). M
Since the saturation magnetic field of the R element is sufficiently smaller than the signal magnetic field of the magnet 1, the resistance value change of the MR element group with respect to the signal magnetic field of the magnet 1 is as shown in FIG. 3(a).

Therefore, constant current I. These elements 6. A similar output change can be obtained by energizing . That is, a pulse-like output is obtained every phase angle π/(n + 1) of the magnetic field, and a pulse-like output with a different pulse level is obtained every phase angle π of the magnetic field. When shaping the waveform indicating the output change obtained in this way to create a rectangular wave, by appropriately selecting the reference voltage, it is possible to easily generate the multiple types of waves shown in Figures 3(b) and 3(C). You can get the output signal.

Further, this is not limited to the width, but the same effect can be obtained if the saturation magnetic field is changed by controlling the thickness 9 composition and the change in resistance value shown in FIG. 3(a) is obtained.

FIG. 4 is a sectional view showing the configuration of an encoder as a second embodiment of the present invention, in which an MR element is mounted on the inner circumferential surface of a cylindrical substrate 9 facing a cylindrical magnet 8 magnetized on the outer circumference. It is formed. The MR element is the same as in the first embodiment described above, and in the signal magnetic field shown in FIG. 1(c), the MR element 6.6' with different widths and lengths is
The MR elements 6 are arranged at a pitch of (n-0°1.2...), and the MR elements 6 are arranged at a pitch of π. These MR elements 6.6' are all connected in series. Also in this example, the change in resistance value of the MR element with respect to the signal magnetic field of the magnet 8 is shown in FIGS. 3(a) and 3(b).
, (C).

FIG. 5 is a diagram showing the concept of the third embodiment of the present invention. In this embodiment, the magnet 11 moves linearly,
Output pulses are obtained from the MR element group 12 as the magnet moves. The magnet 11 is magnetized so that N poles and S poles are alternately arranged as shown in the figure on the surface facing the MR element group 12, and the MR element group 12 has an MR element 12a and an MR element 12b of different lengths. are connected in series, and as a result, a pulse-like output is obtained at a predetermined period, and pulses with different widths are obtained at a period longer than the predetermined period.

The encoder as described above is used, for example, as a speed detector for a flat brushless motor. This allows the main magnet of the motor to be the detected magnet.
If a pattern of MR elements as described above is arranged opposite to the magnet, there is no need to provide a special magnet for speed detection, and the motor can be made smaller and the number of parts can be reduced.

In the encoders of the embodiments described above, the number of output pulses can be increased without increasing the number of magnetized magnets, and the resolution can be easily increased. In addition, multiple sets of MRs arranged to obtain the same output pulse
By connecting the elements in series, it is possible to reduce deterioration in output signal accuracy due to physical factors such as eccentricity and uneven magnetization.

[Effects of the Invention] As explained above, the present invention has different saturation magnetic fields of MR elements according to predetermined rules.
We were able to obtain multiple types of signals. As a result, MR
Even if the relative speeds of the element group and the facing macnet are different, for example, if the pattern of the MR element can output signals of two types of frequencies: a signal of a predetermined frequency and a signal of twice the frequency. , it is possible to obtain signals with the same number of frequencies even when the relative velocity becomes l/k.

In addition, since multiple signals can be obtained from one MR element group, there is no need to newly arrange patterns for this purpose.
This is effective in downsizing the encoder.

[Brief explanation of the drawing]

FIGS. 1(a), (b), (C), and (d) are the first embodiments of the present invention.
FIG. 1(a) is a sectional view, FIG. 1(b), (C
) is a diagram showing how the magnet is magnetized, and (d) of the same diagram is M
A diagram showing the pattern of the R element, FIG. 2 is a diagram for explaining the output obtained from each MR element, and FIG. 3 is a diagram showing the MR element of the present invention.
FIG. 4 is a cross-sectional view showing the configuration of an encoder as a second embodiment of the present invention, and FIG. 5 is a diagram showing a change in resistance value of an element. It is a figure showing a way of thinking. In the figure. l, 9: Substrate 2.8. II: Magnet 3.10
: Stator yoke 4: Rotating board 5: Rotating shaft 6.12: MR element 7: Conductor agent Patent attorney 1) Haru Kitatake (Q) (C) Fig. 1 Fig. 1 (d) (a) (b) (C) Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) An encoder device that detects the relative position of a detected object and a detected object, the detected object being magnetized at a predetermined pitch;
the saturation magnetic field is sufficiently smaller than the magnetizing magnetic field of the detected object;
A detection object in which a plurality of magnetoresistive elements arranged in parallel at a pitch smaller than the magnetization pitch are opposed to the object to be detected, and the saturation magnetic fields of the plurality of magnetoresistive elements arranged in parallel are made different according to a predetermined rule. An encoder device characterized by being equipped with. (2) Width and length of multiple parallel magnetoresistive elements,
The encoder device according to claim 1, wherein the encoder device has a different width or composition.